#' @title Pseudo-time ordering
#' @description This function takes the exact output of exprmclust function and
#'   construct Pseudo-time ordering by mapping all cells onto the path that
#'   connects cluster centers.
#' @param object \code{DISCBIO} class object.
#' @param quiet if `TRUE`, suppresses intermediary output
#' @param export if `TRUE`, exports order table to csv
#' @param filename Name of the exported file (if `export=TRUE`)
#' @importFrom TSCAN TSCANorder
#' @return The DISCBIO-class object input with the kordering slot filled.
setGeneric("pseudoTimeOrdering", function(
    object,
    quiet = FALSE,
    export = FALSE,
    filename = "Cellular_pseudo-time_ordering") {
  standardGeneric("pseudoTimeOrdering")
})

#' @export
#' @rdname pseudoTimeOrdering
setMethod(
  "pseudoTimeOrdering",
  signature = "DISCBIO",
  definition = function(object, quiet, export, filename) {
    # ======================================================================
    # Validating
    # ======================================================================
    ran_k <- length(object@kmeans$kpart) > 0
    ran_m <- length(object@MBclusters) > 0
    if (ran_k) {
      Obj <- object@fdata
      Names <- object@cpart
      lpsmclust <- Exprmclust(Obj, K = 4, reduce = FALSE, cluster = Names)
      lpsorder <- TSCANorder(lpsmclust)
    } else if (ran_m) {
      Obj <- object@fdata
      Names <- names(object@MBclusters$clusterid)
      lpsmclust <- object@MBclusters
      lpsorder <- TSCANorder(lpsmclust)
    } else {
      stop("run clustexp before this pseudoTimeOrdering")
    }
    # ======================================================================
    # Ordering
    # ======================================================================
    sampleNames <- colnames(Obj)
    orderID <- lpsorder
    order <- seq_len(length(lpsorder))
    orderTable <- data.frame(order, orderID)
    if (export) write.csv(orderTable, file = paste0(filename, ".csv"))
    if (!quiet) print(orderTable)
    FinalOrder <- orderTable[match(sampleNames, orderTable$orderID), ]
    out_order <- FinalOrder[, 1]
    names(out_order) <- names(Names)
    if (ran_k) {
      object@kordering <- out_order
    } else if (ran_m) {
      object@MBordering <- out_order
    }
    return(object)
  }
)